How to take care of a paralyzed parrot?

It sounds as though he has what is called a splayed leg. It is caused by improper bed when they growing up. It is easily fixed when the bird is quite young but almost impossible when it is older. The leg will be held straight or off to the side and the joints are rigid and do not bend. The bird can survive very well. You will need to provide ladders,different size perches,a few rope type toys within easy reach to hang onto, and a platform perch for him to sleep on if he desires.Keep toenails clipped and check any ropes or string perches every time you go by the cage to prevent the bird getting caught up. Remove and trim any that don't look good promptly or discard.Make sure he can access food and water. I have a friend that had a keet like that. It lived over 10 years and raised a family. Good luck. Did not your vet give you any possible cures or advice on how to take care of it? I had a bird with with crippled feet and a rather large cholla cactus perch worked very well . Watch your bird carefully and you will come up with a few solutions on your own. was your vet an avian vet? If not find one. They can help when the bird is young.